Proton Therapy For Prostate Cancer

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My friend is getting treated with proton therapy. What is the difference between that and regular radiation? Is it better?

Neha Vapiwala , MD, Senior Editor of OncoLink and Chief Resident in the Department of Radiation Oncology at the Hospital of the University of Pennsylvania, responds:

Proton beams are considered a form of particle therapy and a way of delivering external beam radiation therapy. So-called "regular radiation" is also external beam radiation that consists of high-energy x-rays rather than particles. The main difference protons and X-rays is a physical one: X-rays used in cancer therapy are electromagnetic waves that are highly penetrating, and will deliver dose throughout any volume of tissue irradiated, regardless of thickness. So x-rays tend to deliver substantial doses of radiation both on the way in and on the way out on the way to the tumor volume. Unlike with X-rays, the absorbed dose of a proton beam increases very gradually as it travels through the body, and then suddenly peaks at the end (this is known as the Bragg Peak). A proton beam can be directed so that the Bragg Peak occurs inside the tumor volume, something that cannot be done with X-rays. As a result, the dose around the tumor volume is much less than the tumor itself. Side effects, both acute and long-term, can thus possibly be reduced with proton beams due to the sparing of normal tissues that are situated around the tumor. Ultimately this depends on the type, size and location of the tumor, and proton therapy is not appropriate or preferred for all patients.